testing: improve QueueByTwoStacksTest (#6416)

testing: improve QueueByTwoStacksTest

src/test/java/com/thealgorithms/datastructures/queues/QueueByTwoStacksTest.java

@@ -33,19 +33,19 @@ public class QueueByTwoStacksTest {
         queue.put(10);
         queue.put(20);
         queue.put(30);
-        assertEquals(10, queue.get()); // First item out
+        assertEquals(10, queue.get());
-        assertEquals(20, queue.get()); // Second item out
+        assertEquals(20, queue.get());
-        assertEquals(30, queue.get()); // Third item out
+        assertEquals(30, queue.get());
     }
 
     @Test
     public void testInterleavedOperations() {
         queue.put(10);
         queue.put(20);
-        assertEquals(10, queue.get()); // Dequeue first item
+        assertEquals(10, queue.get());
         queue.put(30);
-        assertEquals(20, queue.get()); // Dequeue second item
+        assertEquals(20, queue.get());
-        assertEquals(30, queue.get()); // Dequeue third item
+        assertEquals(30, queue.get());
     }
 
     @Test
@@ -62,8 +62,76 @@ public class QueueByTwoStacksTest {
 
     @Test
     public void testEmptyQueueException() {
-        assertThrows(NoSuchElementException.class, () -> {
+        assertThrows(NoSuchElementException.class, () -> queue.get());
-            queue.get(); // Attempting to dequeue from empty queue
+    }
-        });
+
+    @Test
+    public void testDequeueAllElements() {
+        for (int i = 1; i <= 5; i++) {
+            queue.put(i);
+        }
+        for (int i = 1; i <= 5; i++) {
+            assertEquals(i, queue.get());
+        }
+        assertEquals(0, queue.size());
+    }
+
+    @Test
+    public void testLargeNumberOfOperations() {
+        int n = 1000;
+        for (int i = 0; i < n; i++) {
+            queue.put(i);
+        }
+        for (int i = 0; i < n; i++) {
+            assertEquals(i, queue.get());
+        }
+        assertEquals(0, queue.size());
+    }
+
+    @Test
+    public void testRefillDuringDequeue() {
+        queue.put(1);
+        queue.put(2);
+        assertEquals(1, queue.get());
+        queue.put(3);
+        queue.put(4);
+        assertEquals(2, queue.get());
+        assertEquals(3, queue.get());
+        assertEquals(4, queue.get());
+    }
+
+    @Test
+    public void testAlternatingPutAndGet() {
+        queue.put(1);
+        assertEquals(1, queue.get());
+        queue.put(2);
+        queue.put(3);
+        assertEquals(2, queue.get());
+        queue.put(4);
+        assertEquals(3, queue.get());
+        assertEquals(4, queue.get());
+    }
+
+    @Test
+    public void testSizeStability() {
+        queue.put(100);
+        int size1 = queue.size();
+        int size2 = queue.size();
+        assertEquals(size1, size2);
+    }
+
+    @Test
+    public void testMultipleEmptyDequeues() {
+        assertThrows(NoSuchElementException.class, () -> queue.get());
+        assertThrows(NoSuchElementException.class, () -> queue.get());
+    }
+
+    @Test
+    public void testQueueWithStrings() {
+        QueueByTwoStacks<String> stringQueue = new QueueByTwoStacks<>();
+        stringQueue.put("a");
+        stringQueue.put("b");
+        assertEquals("a", stringQueue.get());
+        assertEquals("b", stringQueue.get());
     }
 }